Ice and water shield requirements in Michigan are something every homeowner should understand before replacing their roof. Most people know that ice and water shield helps prevent leaks. What they don’t know is that installing it in the wrong places, or not extending it far enough, can leave a roof vulnerable.
Here in Metro Detroit, we deal with snow, freezing rain, ice dams, and temperatures that regularly move above and below freezing.
Those conditions make proper roof underlayment especially important.
At Level Up Improvement, we believe homeowners should know what’s going underneath their shingles, not just what the finished roof will look like.
Let’s break down how much ice and water shield your roof needs, where it should be installed, and what contractors sometimes overlook.
What Is Ice and Water Shield?
Ice and water shield is a self-adhering waterproof roofing membrane installed directly over the roof decking, beneath the shingles.
Unlike standard synthetic underlayment, which primarily acts as a secondary water-resistant layer, ice and water shield is designed to help protect vulnerable areas against water backing up beneath the roofing.
Many products also seal around properly driven roofing nails.
CertainTeed’s version is called WinterGuard, although other manufacturers offer similar products.
Ice and water shield is especially useful where water is more likely to collect, back up, or enter through vulnerable roof details.
However, it’s not a replacement for properly installed shingles, flashing, or attic ventilation.
How Far Up the Roof Should Ice and Water Shield Go?
This is probably the most important part of the entire article.
For roofs subject to ice-barrier requirements, the standard residential code approach is to extend the membrane from the lower roof edge to at least 24 inches inside the exterior wall line.
Notice what that says.
It does not say 24 inches up the roof.
It says 24 inches inside the exterior wall line.
Those are two very different measurements.
Why One 3-Foot Roll Often Isn’t Enough
Most ice and water shield comes in rolls approximately 36 inches wide.
Some contractors install one course along the bottom of the roof and move on.
But consider a home with a 12-inch roof overhang.
The first 12 inches of horizontal coverage may only reach the outside of the wall. The membrane then needs to extend another 24 inches inward.
And because the roof is sloped, the actual distance along the roof surface is longer.
Depending on the pitch and overhang, one 36-inch course may fall well short.
For example, on a 6/12 roof with a 12-inch horizontal overhang, reaching 24 inches inside the wall requires approximately 40 inches of coverage measured along the roof slope, even before allowing for installation details.
That means a single 36-inch roll wouldn’t be enough.
This is one of the biggest details we think homeowners should ask about when comparing roofing estimates.
A contractor might tell you they’re installing ice and water shield without explaining how far it will extend.
Those details matter.
Where Should Ice and Water Shield Be Installed?
There are several areas where ice and water shield deserves attention.
1. Along the Eaves
Eaves are the lower edges of your roof, where gutters are typically installed.
These areas are especially vulnerable to ice dams.
During winter, heat escaping from a home can contribute to snow melting higher up the roof. That water may refreeze when it reaches the colder eaves.
As ice builds up, water can back up beneath the shingles.
Ice and water shield provides an additional layer of protection against that water intrusion.
For Michigan homes, proper eave coverage is one of the most important parts of the roofing system.
2. In Roof Valleys
A valley is where two roof slopes meet.
Think about what happens during heavy rain or snowmelt.
Water from both roof sections flows into the same channel.
That makes valleys some of the busiest drainage areas on a roof.
Installing a compatible waterproof membrane beneath the valley system provides extra protection.
The membrane must be installed correctly, with proper overlaps and integration into the surrounding underlayment.
Valley protection should also work with the type of valley being installed, whether that’s an open metal valley or a closed shingle valley.
3. Around Chimneys
Chimneys create several vulnerable transitions where the roof meets a vertical structure.
These areas require correctly installed flashing, including step flashing and counterflashing where appropriate.
Ice and water shield can provide additional protection beneath those details.
However, simply sticking membrane around a chimney doesn’t replace proper metal flashing.
If a contractor relies on roofing cement or sealant instead of installing the flashing correctly, that’s something homeowners should question.
4. Around Skylights
Skylights are another area where water intrusion can occur.
They need properly integrated flashing and underlayment.
A compatible self-adhered membrane is often used around the opening as part of the manufacturer’s installation system.
The important thing is following the skylight manufacturer’s flashing instructions.
More membrane doesn’t automatically make a poorly flashed skylight watertight.
5. Around Plumbing Vents and Roof Penetrations
Every opening through the roof deserves attention.
That includes plumbing vents, exhaust vents, and other penetrations.
Ice and water shield can help provide secondary protection around these areas.
But the correct flashing boot or roof penetration assembly is still necessary.
The membrane and flashing must work together to direct water down and off the roof.
6. At Roof-to-Wall Intersections
When a lower roof meets a wall, water can collect along that transition.
Snow can also accumulate against the wall during winter.
These areas deserve careful attention because leaks can travel behind siding or other exterior materials before becoming visible inside the house.
Proper step flashing, kick-out flashing where needed, and compatible underlayment are all important.
This is another place where the work you can’t see matters just as much as the shingles.
Does a 3/12 Roof Need Ice and Water Shield Over the Entire Roof?
This is an especially important question for Michigan homeowners.
A 3/12 roof is considered a low-slope roof for asphalt shingle installation.
That means the roof rises 3 inches for every 12 inches of horizontal distance.
Water drains more slowly on a 3/12 roof than it does on a steeper roof.
As a result, low-slope roofs need additional underlayment protection.
What Does CertainTeed Require?
For CertainTeed asphalt shingles installed on slopes from 2/12 to less than 4/12, the manufacturer’s published instructions call for WinterGuard waterproofing underlayment, or an approved equivalent, over the entire roof deck.
For a Michigan roof, that can mean full ice and water shield coverage rather than just strips along the eaves and valleys.
This is especially important when you’re considering CertainTeed Landmark or Landmark PRO shingles.
Always check the current instructions for the exact product and warranty system being installed.
A contractor shouldn’t treat a 3/12 roof the same way as a standard 6/12 roof.
What About a 4/12 Roof?
A 4/12 roof generally falls into the standard-slope category for asphalt shingles.
That means the full-deck low-slope underlayment requirement does not automatically apply.
However, ice barrier protection is still needed where required by code and the manufacturer’s instructions.
A roof can also have several different pitches.
For example, a house might have a 6/12 main roof with a 3/12 section over a porch or addition.
Each roof section needs to be evaluated based on its actual slope.
Should You Cover the Entire Roof With Ice and Water Shield?
Some homeowners assume that if ice and water shield is good, covering the entire roof must be better.
Not necessarily.
Full-deck coverage can be appropriate or required for certain roof systems, especially low-slope applications.
But it isn’t automatically necessary for every standard-slope roof.
One consideration is moisture management.
Self-adhered waterproof membranes generally have low vapor permeability. Covering the entire roof deck can reduce its ability to dry outward.
That makes attic air sealing, insulation, and ventilation especially important.
Full coverage also adds material and labor costs.
The best approach is to follow the roofing manufacturer’s instructions, meet applicable code requirements, and evaluate the home’s specific conditions.
Does Ice and Water Shield Prevent Ice Dams?
No.
Ice and water shield helps protect against water intrusion caused by ice dams, but it doesn’t stop the dams from forming.
Ice dams are often related to heat escaping into the attic, uneven roof temperatures, snow accumulation, and freezing conditions.
Reducing the risk usually involves a combination of:
- Proper attic air sealing
- Adequate insulation
- Balanced intake and exhaust ventilation where appropriate
- Correct roof drainage
- Properly installed roofing and flashing
We discuss several of these issues in our guide to Michigan winter roof preparation.
The key point is that ice and water shield is one part of the solution, not the entire solution.
What Do Roofing Contractors Sometimes Overlook?
There are a few details homeowners should pay attention to when reviewing an estimate or watching a roof replacement.
Not Measuring Past the Exterior Wall
As we mentioned earlier, one 36-inch course may not extend far enough.
The correct measurement depends on the roof pitch and overhang.
Ignoring Low-Slope Roof Sections
A small porch, addition, or garage roof might have a different pitch than the rest of the house.
Those areas shouldn’t be overlooked just because the main roof has a standard slope.
Poorly Installed Membrane Overlaps
Self-adhered membranes need the correct overlaps and installation conditions.
If seams aren’t properly adhered, water can find its way through.
Covering Damaged Roof Decking
Ice and water shield should be installed over a suitable roof deck.
If the wood underneath is rotten, soft, or otherwise compromised, covering it with new materials doesn’t fix the problem.
We explain why this matters in our article about roof decking types.
Treating Ice and Water Shield as a Substitute for Flashing
Even a high-quality membrane cannot compensate for missing or improperly installed flashing.
Chimneys, sidewalls, skylights, and roof penetrations still need the correct flashing assemblies.
Forgetting About Ventilation
When a roof receives extensive self-adhered membrane coverage, moisture management becomes especially important.
A properly designed attic system helps control moisture and reduce conditions that contribute to winter roofing problems.
How Much Ice and Water Shield Should Be Included in Your Roofing Estimate?
The amount depends on your home’s roof design.
A simple gable roof might need protection primarily along the eaves and at penetrations.
A more complicated roof with multiple valleys, dormers, skylights, and low-slope sections can require considerably more.
The roof’s pitch and overhang also affect how many courses are necessary.
Instead of asking only how many rolls the contractor plans to use, ask where the membrane will go and how far it will extend.
That’s a much better way to understand what you’re paying for.
Questions to Ask Your Roofing Contractor
Before signing a roofing contract, consider asking:
- How far past the exterior wall will the ice and water shield extend?
- Will one course be enough, or will my roof need two?
- Are all roof valleys receiving waterproof membrane protection?
- How will you protect the areas around chimneys and skylights?
- Do any sections of my roof have a pitch below 4/12?
- Does the shingle manufacturer require full-deck waterproof underlayment on those sections?
- What happens if damaged roof decking is discovered?
- Will the installation meet the manufacturer’s warranty requirements?
A good contractor should be able to explain these details without making you feel like you’re asking too many questions.
Ice and Water Shield Requirements in Michigan: The Bottom Line
The most important thing to remember about ice and water shield requirements in Michigan is that proper coverage depends on more than the width of a roll.
On roofs where ice barriers are required, the membrane generally needs to extend at least 24 inches inside the exterior wall line.
Valleys, chimneys, skylights, and other vulnerable areas may need additional protection.
Low-slope roof sections require special attention, and CertainTeed’s published instructions call for full-deck waterproofing underlayment on applicable slopes below 4/12.
At Level Up Improvement, we believe homeowners deserve to understand how their roofing system is being installed.
We’re a family-owned exterior remodeling company serving Royal Oak, Birmingham, Waterford, Troy, Ferndale, Bloomfield Hills, Novi, and surrounding Metro Detroit communities.
If you’re planning a roof replacement, we’d be happy to inspect your roof, explain the underlayment requirements, and help you understand your options.
Learn more about our Michigan roofing services or contact Level Up Improvement.
Do it right!